Foreign-backed militants fighting government forces in Syria have reportedly killed at least 30 civilians in the northwestern province of Idlib.

Al-Qaeda-linked militants of the Islamic State of Iraq and the Levant fired a series of mortar shells on Kafteen village, leaving 30 people dead and several others injured.

In a separate incident, the extremists fired mortar shells on a town in the province.

The attack primarily targeted a police station and led to the injury of a number of civilians.

Locals said they saw some people vomiting after the shelling, which could be a sign of a chemical attack.

A recent British defense study shows that about 100,000 foreign-backed militants, fragmented into 1,000 groups, are fighting in Syria against the government and people.

The extracts of the study by defense consultancy IHS Jane's were published on September 16 in The Daily Telegraph.

IHS Jane's estimates that some 10,000 militants are fighting for groups affiliated with al-Qaeda such as al-Nusra Front and the rest fight for different militant groups.

The analysis also said that a large number of extremists from foreign countries are also active in Syria.

Syria has been gripped by deadly unrest since March 2011. According to reports, the Western powers and their regional allies -- especially Qatar, Saudi Arabia, and Turkey -- are supporting the militants operating inside Syria.

According to the United Nations, more than 100,000 people have been killed and a total of 7.8 million of others displaced due to the violence.